rdwanjr

Greetings all,
I have a 2001 W220 S500 with ABC suspension. I've watched the videos that show how to remove and replace the hydraulic fluid without using a special tool and without using the Star Mercedes Computer program.
Many thanks to ''shooffnyc'' for the excellent tutorial. https://www.youtube.com/watch?v=VsWXcPjBj2M[/URL]
My question is this:
If I replaced the suspension components such as those struts or the accumulators or the valve blocks is this sort of drain and replace procedure good enough to get things up and running again?
My mechanic tells me that the system would have to be blead and that involves the Mercedes Star System and performing the "Rodeo”.
Thanks in advance,
Richard

Welwynnick

You have to be very careful about what you read with ABC. It's more difficult to maintain than conventional suspension for sure, but there's no black magic to it, only variable degrees of understanding, even amongst professionals.

You definitely need a special bleed procedure if air gets in the tandem pump, typically when the fluid reservoir is empty. But otherwise, there's no bleeding to do, just drive around and be sure to keep it topped up.

There's certainly no need to bleed after a strut replacement. Small air bubbles will get in the return line that goes back to the reservoir, where they slowly float to the surface. The feed to the pump is taken from the bottom of the reservoir, and is safe if the reservoir is full.

Note that there two level markers on the ABC dipstick - the upper one is for engine off, and the lower is for engine running. Given a short time for stabilisation, the level should be correct for both conditions, which indicates the accumulators are taking the right volume of fluid when they're pressurized.

Nick

jkm5022

Nick
You made a comment that the level of fluid in on and off condition indicate that the accumulators are ok. The other day I checked the levels and the on level was correct but the off level was low. I filled it up to proper in off condition. Is this indicating a problem?

tusabes

There's two theories on abc drain and refill - the easy way where you just put the return hose from the reservoir into a bucket , while you fill the reservoir with fresh fluid until it runs clear/light green


then there's the difficult way where you bleed from each strut , the benefit is this will be a more complete flush , that flushes each strut , but it also has greater risks of something going wrong , more than just the reservoir drain and fill

Welwynnick

That suggests one or more of your accumulators are weak.

It's difficult to diagnose which one. There are three ways:

Throw new parts at the car and hope you find the bad one.

Does the suspension make a distinct whining/droning sound at low engine speeds that sounds like a worn transmission, and which disappears when you remove the aux drive belt (from a cold engine!)? If so, its probably the vibration damper on the pressure control valve behind the RHS front wheel. If not, that damper is probably OK.

Remove each damper in turn and push a pen or suchlike in the hole. If the rubber diaphragm offers resistance, it's probably OK.

Nick

Welwynnick

It's not so easy, but I favour the method where you drain from each strut, because that's where all the dirty oil is, and it helps to avoid having that oil circulate round the pump and valves.

Nick

David Alvey

I did the same to my S55 and found the rubber nipplie covers at the drain ports were too dry to re-use. You can purchase replacements on Ebay or Amazon in packs of 25.